Plating catalyst liquid, plating method, and method for producing laminate having metal film

ABSTRACT

A plating catalyst liquid which places little burden on the environment, which does not roughen the surface of a plating target, which can be easily controlled for the amount of plating catalyst applied and which is at low risk of inflammation and is highly safe, and a plating method using the plating catalyst are provided. The plating catalyst liquid includes a palladium compound, water, and a water-soluble combustible liquid serving as a combustible liquid ingredient, has a flash point of 40° C. or more and contains the water-soluble combustible liquid in an amount of 0.1 to 40 wt %.

TECHNICAL FIELD

The present invention relates to a plating catalyst liquid, a plating method using the plating catalyst liquid and a method for producing a laminate having a metal film with the use of the plating catalyst liquid.

BACKGROUND ART

Recently, the technique of forming a metal film by plating on a surface of a material has been utilized in various fields for functional or decorative purposes. For example, the resin moldings such as automobile parts are plated with metals such as copper and nickel to add a touch of class and an aesthetic value thereto. In addition, the technique of obtaining a desirably patterned metal film after the formation of a metal film by plating on an insulating film is widely used to manufacture electronic components and semiconductor devices. This technique is used in, for example, printed circuit boards employed in electronic devices and electromagnetic interference shielding films employed in plasma displays.

A “substractive” process and a “semi-additive” process are used to manufacture materials having such a patterned metal film.

The substractive process is a process in which a layer which is photosensitive to irradiation with actinic rays is first provided on a metal film formed on a surface of a substrate; the photosensitive layer is then exposed imagewise and developed to form a patterned resist image; the metal film in a region having no resist image is then etched to form a metal pattern; and finally the resist image is peeled off.

On the other hand, the semi-additive process is a process in which a power supply layer is formed by any method on a surface of a substrate such as an insulating resin film; a layer which is photosensitive to irradiation with actinic rays is then formed on the power supply layer; the photosensitive layer is exposed imagewise and developed to form a patterned resist image; electroplating is then performed as an electric current is flowed through the power supply layer to form metal wiring in the resist-free portions; and the part of the power supply layer having no metal wiring is etched to form a metal pattern. The power supply layer formed by this technique is formed by plating using a plating catalyst liquid. This technique considerably reduces the amount of metal removed by etching and is therefore capable of suppressing excessive etching of the lateral surfaces of wiring as seen in the subtractive process and is advantageous to form micro-wiring.

In the metal pattern formed by these processes, however, the adhesion between the substrate and the metal film is achieved by the anchor effect produced by forming irregularities at the surface of the substrate. Therefore, when used as metal wiring, the metal pattern suffered from poor radio frequency characteristics due to the irregularities at the interface between the metal pattern and the substrate. What is more, roughening of the substrate surface required treatment of the substrate surface with a strong acid such as chromic acid, which complicated the step and led to environmental problems such as liquid waste disposal.

In order to solve these problems, a method for achieving a strong adhesion with metal wiring while keeping a substrate surface flat and smooth is proposed (Non-Patent Literature 1). More specifically, this surface treatment involves performing a plasma treatment on the substrate surface to introduce a polymerization initiating group on the substrate surface and polymerizing a monomer from the polymerization initiating group to form a surface graft polymer having a polar group on the substrate surface. This method enables the adhesion between the substrate and the metal film to be improved without roughening the surface of the substrate. On the other hand, the graft polymer has a polar group in this method and therefore moisture is easily absorbed or removed due to temperature or humidity changes and as a result the metal film formed or the substrate may be deformed. In addition, in cases where a substrate modified with such a polar group-containing graft polymer is used to perform substrate metalization, a fault due to water absorption in the electrical wiring manufacturing process and an electrical fault of electrical wiring itself may occur.

In a method for obviating these problems, for example, a hydrophobic substrate having a catalyst-adsorbing, hydrophobic patterned resin layer formed thereon is preferably used as the wiring substrate. In this case, a certain amount of the plating catalyst liquid must permeate the catalyst-adsorbing, hydrophobic patterned resin layer.

In this regard, use of a non-aqueous plating catalyst liquid is proposed as a method of improving the plating properties while keeping the hydrophobicity and surface flatness of a plating target (Patent Literature 1). Patent Literature 1 discloses using as the plating catalyst liquid a colloidal dispersion of a reduced metal which is obtained by reducing a metal salt or a metal complex in a mixed solution containing a lower alcohol and an aprotic polar compound.

CITATION LIST Patent Literature

Patent Literature 1: JP 1-315334 A

Non-Patent Literature

Non-Patent Literature 1: Advanced Materials, 2000, Vol. 12, no. 20, 1481-1494

SUMMARY OF INVENTION Technical Problems

However, the plating catalyst liquid containing a non-aqueous solvent as described in Patent Literature 1 is an aqueous inflammable liquid and therefore is at high risk of inflammation and needs equipment which meets predetermined requirements on the storage and handling. Particularly in the case of high-volume industrial production, the foregoing plating catalyst liquid requires huge capital investments and is not preferred from the economical point of view. Use of a large quantity of hazardous materials increases the environmental burdens and is also not preferred to ensure the safety of workers.

The inventors of the invention have made an intensive study and as a result found that use of the non-aqueous plating catalyst liquid as described in Patent Literature 1 may hinder the control of the amount of deposition on a hydrophobic plating target. Therefore, the plating catalyst also adheres to unnecessary portions during the formation of a patterned film by plating, which may hinder the formation of a desired pattern.

In addition, the amount of deposits formed by plating was also difficult to control in cases where the non-aqueous plating catalyst liquid as described in Patent Literature 1 is used to form the power supply layer upon the formation of wiring by the foregoing semi-additive process. As a result, it was also found that it may be difficult to remove catalyst or metal residues having adhered to a plating target upon the removal of the power supply layer by metal etching. Therefore, upon the formation of a patterned film by plating, metal may remain between interconnects, leading to a decrease in the insulation resistance, whereby desired electrical characteristics cannot be obtained.

In view of the situation as described above, an object of the invention is to provide a plating catalyst liquid which places little burden on the environment, which does not roughen the surface of a plating target, which can be easily controlled for the amount of plating catalyst applied and which is at low risk of inflammation and is highly safe. Another object of the invention is to provide a plating method using the plating catalyst.

Solution to Problems

The inventors of the invention have made an intensive study to achieve the objects and as a result found that the objects of the invention are achieved by the characteristic features described in (1) to (12) below.

-   (1) A plating catalyst liquid comprising: a palladium compound;     water; and a water-soluble combustible liquid serving as a     combustible liquid ingredient, wherein the catalyst liquid has a     flash point of 40° C. or more and contains the water-soluble     combustible liquid in an amount of 0.1 to 40 wt %. -   (2) The plating catalyst liquid according to (1), wherein the     water-soluble combustible liquid is a water-soluble organic solvent     having no primary or secondary hydroxyl group. -   (3) The plating catalyst liquid according to (1) or (2) which     further comprises an acid. -   (4) The plating catalyst liquid according to any one of (1) to (3),     wherein a plating target is made of a hydrophobic resin having a     functional group capable of interacting with a plating catalyst or     its precursor. -   (5) The plating catalyst liquid according to (4), wherein the     hydrophobic resin is a cured product of a photosensitive resin     composition containing a polymer which has the functional group     capable of interacting with the plating catalyst or its precursor     and a polymerizable group. -   (6) The plating catalyst liquid according to (5), wherein the     polymer is a copolymer containing recurring units represented by     general formulas (1) and (2):

(in general formula (1), R¹ to R⁴ are each independently a hydrogen atom or an optionally substituted alkyl group, Z and Y are each independently a single bond or an optionally substituted divalent organic group, and L¹ is an optionally substituted divalent organic group, and in general formula (2), R⁵ is a hydrogen atom or an optionally substituted alkyl group, X is a single bond or an optionally substituted divalent organic group, and L² is an optionally substituted divalent organic group).

-   (7) A plating method comprising:

a catalyst applying step for applying a plating catalyst or its precursor to a plating target by contacting the plating catalyst liquid according to any one of (1) to (3) with the plating target; and

a plating step for plating the plating target obtained in the catalyst applying step.

-   (8) The plating method according to (7), wherein the plating target     is made of a hydrophobic resin having a functional group capable of     interacting with the plating catalyst or its precursor. -   (9) The plating method according to (8), wherein the hydrophobic     resin is a cured product of a photosensitive resin composition     containing a polymer which has the functional group capable of     interacting with the plating catalyst or its precursor and a     polymerizable group. -   (10) The plating method according to (9), wherein the polymer is a     copolymer containing recurring units represented by general     formulas (1) and (2):

(in general formula (1), R¹ to R⁴ are each independently a hydrogen atom or an optionally substituted alkyl group, Z and Y are each independently a single bond or an optionally substituted divalent organic group, and L¹ is an optionally substituted divalent organic group, and in general formula (2), R⁵ is a hydrogen atom or an optionally substituted alkyl group, X is a single bond or an optionally substituted divalent organic group, and L² is an optionally substituted divalent organic group).

-   (11) A method for producing a laminate having a metal film, the     method comprising:

an application step in which a photosensitive resin composition containing a polymer having a functional group capable of interacting with a plating catalyst or its precursor and a polymerizable group is applied onto a substrate to form a photosensitive resin composition layer on the substrate;

an exposure step in which the photosensitive resin composition layer is exposed in a pattern shape to form a patterned cured layer;

a development step in which part of the photosensitive resin composition layer unexposed in the exposure step is removed;

a catalyst applying step in which the patterned cured layer obtained in the development step is contacted with the plating catalyst liquid according to (1) to (3) to apply the plating catalyst or its precursor to the cured layer; and

a plating step in which a plating treatment is performed on the cured layer to which the plating catalyst or its precursor was applied in the catalyst applying step.

-   (12) The method for producing a laminate having a metal film     according to (11), wherein the plating treatment in the plating step     is one in which electroless plating is followed by electroplating.

Advantageous Effects of Invention

The invention can provide a plating catalyst liquid which ensures high work safety, which places little burden on the environment, which does not roughen the surface of a plating target, and which can be highly controlled for the amount of plating catalyst applied, thus leading to excellent wiring formability, and which is not included in the hazardous materials defined in the Category IV under the Fire Service Act, and a plating method using the plating catalyst.

Particularly when containing an acid, the plating catalyst has more improved storage stability. Use of a water-soluble organic solvent having no primary or secondary hydroxyl group improves the long-term storage stability of the plating catalyst liquid.

DESCRIPTION OF EMBODIMENTS

The plating catalyst liquid, the plating method using the plating catalyst liquid and the method for producing a laminate having a metal film with the use of the plating catalyst liquid according to the invention are described below.

The plating catalyst liquid and the plating target for which the catalyst liquid is used are first described.

[Plating Catalyst Liquid]

The plating catalyst liquid of the invention includes a palladium compound, water, and a water-soluble combustible liquid serving as a combustible liquid ingredient, has a flash point of 40° C. or more and contains the water-soluble combustible liquid in an amount of 0.1 to 40 wt % with respect to the total amount of the catalyst liquid.

The respective materials for use in the plating catalyst liquid are first described in detail.

[Palladium Compound]

The plating catalyst liquid of the invention contains a palladium compound. The palladium compound serves as an active nucleus during the plating treatment to deposit the metal and functions as the plating catalyst (palladium) or its precursor (palladium ion). The palladium compound is not particularly limited as long as it contains palladium and serves as the nucleus during the plating treatment. Examples thereof include a palladium (II) salt, a palladium (0) complex and a palladium colloid.

Examples of the palladium (II) salt include palladium acetate, palladium chloride, palladium nitrate, palladium bromide, palladium carbonate, palladium sulfate, bis(benzonitrile)dichloropalladium (II), bis(acetonitrile)dichloropalladium (II) and bis(ethylenediamine)palladium (II) chloride. Of these, palladium nitrate, palladium acetate, palladium sulfate and bis(acetonitrile)dichloropalladium (II) are preferred in terms of the ease of handling and the solubility.

Examples of the palladium complex include a tetrakis(triphenylphosphine)palladium complex and a tris(benzylideneacetone)dipalladium complex.

The palladium colloid is composed of palladium (0) particles. The particle size is not particularly limited and is preferably from 5 to 300 nm and more preferably from 10 to 100 nm in terms of the stability in the liquid. The palladium colloid may optionally contain other metals such as tin. An example of the palladium colloid includes a tin-palladium colloid. The palladium colloid may be synthesized by any known method or a commercially available product may be used. For example, the palladium colloid can be prepared by reducing the palladium ion in a solution containing a charged surfactant or a charged protective agent.

The content of the palladium compound in the plating catalyst liquid is from 0.001 to 10 wt %, more preferably from 0.05 to 5 wt % and even more preferably from 0.10 to 1 wt % with respect to the total amount of the catalyst liquid. At too low a content, deposition is difficult to obtain in the plating to be described later, whereas at too high a content, the patterned plating properties and the etching residue removability to be described later may be impaired.

[Water-Soluble Combustible Liquid]

The plating catalyst liquid of the invention contains a water-soluble combustible liquid serving as the combustible liquid ingredient. The water-soluble combustible liquid that may be used in the plating catalyst liquid of the invention is not particularly limited as long as it is a combustible solvent capable of mixing with water at any ratio. Examples thereof include water-soluble organic solvents such as a ketone solvent, an ester solvent, an alcoholic solvent, an ether solvent, an amine solvent, a thiol solvent and a halogen solvent.

Examples of the ketone solvent include 4-hydroxy-4-methyl-2-pentanone, γ-butyrolactone and hydroxyacetone.

Examples of the ester solvents include 2-(2-ethoxyethoxy)ethyl acetate, ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, methyl cellosolve acetate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, methyl glycolate, and ethyl glycolate.

Examples of the alcoholic solvent include ethanol, isopropyl alcohol, normal propyl alcohol, 3-acetyl-1-propanol, 2-(allyloxy)ethanol, 2-aminoethanol, 2-amino-2-methyl-1-propanol, (±)-2-amino-1-propanol, 3-amino-1-propanol, 2-dimethylaminoethanol, 2,3-epoxy-1-propanol, ethylene glycol, 2-fluoroethanol, diacetone alcohol, 2-methylcyclohexanol, 4-hydroxy-4-methyl-2-pentanone, glycerol, 2,2′,2″-nitrilotriethanol, 2-pyridine methanol, 2,2,3,3-tetrafluoro-1-propanol, 2-(2-aminoethoxy)ethanol, 2-[2-(benzyloxy)ethoxy]ethanol, 2,3-butanediol, 2-butoxyethanol, 2,2′-thiodiethanol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-2,4-pentanediol, 1,3-propanediol, diglycerol, 2,2′-methyliminodiethanol and 1,2-pentanediol.

Examples of the ether solvent include bis(2-ethoxyethyl)ether, bis[2-(2-hydroxyethoxy)ethyl]ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, bis(2-methoxyethyl)ether, 2-(2-butoxyethoxy)ethanol, 2-[2-(2-chloroethoxy)ethoxy)ethanol, 2-ethoxyethanol, 2-(2-ethoxyethoxy)ethanol, 2-isobutoxyethanol, 2-(2-isobutoxyethoxy)ethanol, 2-isopropoxyethanol, 2-[2-(2-methoxyethoxy)ethoxy]ethanol, 2-(2-methoxyethoxy)ethanol, 1-ethoxy-2-propanol, 1-methoxy-2-propanol, tripropylene glycol monomethyl ether, methoxyacetic acid and 2-methoxyethanol.

Examples of the glycol solvent include diethylene glycol, triethylene glycol, ethylene glycol, hexaethylene glycol, propylene glycol, dipropylene glycol and tripropylene glycol.

Examples of the amine solvent include N-methyl-2-pyrrolidone and N,N-dimethylformamide.

Examples of the thiol solvent include mercaptoacetic acid and 2-mercaptoethanol.

Examples of the halogen solvent include 3-bromobenzyl alcohol, 2-chloroethanol and 3-chloro-1,2-propanediol.

Exemplary other water-soluble organic solvents that may be used include those illustrated in the table below.

TABLE 1 Acrylic acid 2-(Dimethylamino)ethyl acrylate Acetyl methyl carbinol 1-Amino-4-methylpiperazine Pyridine-3-aldehyde Isobutyric acid Aluminum ethylacetoacetate diisopropylate (water-soluble) Ethyl glycol Ethylene glycol monobutyl ether Ethylene chlorohydrin N-Ethylmorpholine Ethylenediamine 3-Ethoxypropylamine Formic acid (at least 86%) Isoamyl formate Acetic acid 1,4-Diaminobutane 1,2-Diaminopropane 1,3-Diaminopropane 3-Diethylaminopropylamine N,N-Diethylethanolamine Cyclohexylamine N,N-Dimethylacetamide Di-n-butoxy-bis(triethanolaminato)titanium Dimethylaminopropylamine 2-(Dimethylamino)acetoaldehyde dimethyl acetal N,N-Dimethylethanolamine 2,5-Dimethylpyrazine Pyrethrum (protection of stored grain) Hydrazine hydrate (up to 79%) (emulsion) Sodium alcoholate (liquid) Tetramethy1-1,3-diaminopropane Sodium methoxide 1,1,3-trihydrotetrafluoropropanol Ethyl lactate Methyl lactate α-Picoline β-Picoline γ-Picoline Hydrazine (up to 79%) Proprionic acid Propylene chlorohydrin Benzylaminopurine (3% emulsion) Trimethyl borate Methylaminopropylamine N-Methylpiperazine 2-Methylpyrazine 3-Methoxypropylamine 2-Mercaptoethanol Morpholine Diethylenetriamine N,N-dimethylacrylamide Dimethylaminopropyl methacrylamide Dimethylsulfoxide N,N-Dimethylaminopropyl acrylamide (−)-D-Diisopropyl tartrate Hydrazine hydrate (at least 80%) Sulfolane (anhydrous type is solid and Thioglycolic acid nonhazardous) Thiodiglycol Tetraethylenepentamine n-Tetradecane N,N,N′,N′-Tetramethy1-1,6-hexamethylenediamine Triethyl phosphate (TEP) Triethylene glycol Triethylenetetramine Trimethyl phosphate d-Valelolactone Bis(aminopropyl)piperazine Hydrazine (at least 80%) 2-Hydroxyethyl acrylate 2-Hydroxyethylaminopropylamine Hydroxyethyl piperazine 4-Hydroxy-2-butanone Vinyltris(β-methoxyethoxy)silane 2-Pyridinemethanol 3-Pyridinemethanol 4-Pyridinemethanol Pyruvic acid Phenethylamine Formamide 1,3-Butanediol 1,4-Butanediol Butyl diglycol γ-butyrolactone Furfuryl alcohol Hexylene glycol Benzylamine Pentaethylenehexamine Polyethylene glycol diglycidyl ether (n = 13 or less) Polypropylene glycol diglycidyl ether (n = 11 or less) Methacrylic acid 2-Hydroxyethyl methacrylate Methyliminobispropylamine N-Methylethanolamine N-Methyl-N,N-diethanolamine 3-Methyl-3-methoxybutyl acetate β-Mercaptopropionic acid Ethylene glycol monoacetate

The water-soluble combustible liquid of the invention preferably has a boiling point of 80 to 200° C. and more preferably 100 to 200° C. in terms of easier removal of the water-soluble combustible liquid from the plating target to be described later and the stability of the catalyst liquid composition kept by the evaporation of a solvent. Preferred examples of the water-soluble combustible liquid include 1-acetoxy-2-methoxyethane with a boiling point of 145° C., bis(2-ethoxyethyl)ether with a boiling point of 188° C. and bis(2-methoxyethyl)ether with a boiling point of 162° C.

The content of the water-soluble combustible liquid in the plating catalyst liquid of the invention is preferably from 0.1 to 40 wt % and more preferably from 5 to 40 wt % with respect to the total amount of the catalyst liquid in terms of the permeability of the plating target to be described later.

A preferred embodiment of the water-soluble combustible liquid of the invention is a water-soluble organic solvent having no primary or secondary hydroxyl group. Use of the water-soluble organic solvent having no primary or secondary hydroxyl group (preferably an ether solvent having no primary or secondary hydroxyl group) further suppresses the discoloration of the solution while further enhancing the storage stability of the plating catalyst. Use of a water-soluble organic solvent having a primary or secondary hydroxyl group is likely to cause the hydroxyl group to undergo an oxidation reaction due to the palladium compound during the long-term storage to be converted to ketone group, aldehyde group or carboxylic group, thus leading to the discoloration of the solution.

Examples of the water-soluble organic solvent having no primary or secondary hydroxyl group include 4-hydroxy-4-methyl-2-pentanone, 2-(2-ethoxyethoxy)ethyl acetate, 1-acetoxy-2-methoxyethane, bis(2-ethoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, bis(2-methoxyethyl)ether, 2-(dimethylamino)ethyl acrylate and 1-amino-4-methylpiperazine.

In particular, the water-soluble organic solvent is preferably also free from tertiary alcohol having few concerns about the oxidation in terms of the storage stability of the catalyst liquid, and preferred examples thereof include 2-(2-ethoxyethoxy)ethyl acetate, 1-acetoxy-2-methoxyethane, bis(2-ethoxyethyl)ether (also called diethylene glycol diethyl ether), 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether and bis(2-methoxyethyl)ether (also called diethylene glycol dimethyl ether).

The plating catalyst liquid containing the water-soluble combustible liquid that may be used in the invention has a flash point of at least 40° C. The water-soluble combustible liquid for use in the plating catalyst liquid is preferably selected from among those having a flash point of at least 30° C., more preferably at least 40° C. and even more preferably at least 60° C. Within the foregoing range, the plating catalyst liquid has a higher flash point to further improve the work safety.

[Water]

The plating catalyst liquid of the invention contains water. By incorporating water in the plating catalyst liquid, the permeation rate of the plating catalyst or its precursor through the hydrophobic plating target is controlled within a preferred range. The water used is preferably free from impurities. Reverse osmosis (RO) water, deionized water, distilled water and purified water are preferably used, and deionized water and distilled water are more preferred.

The optimal content of water in the plating catalyst liquid of the invention is appropriately selected and the water content is preferably from 35 to 99.899 wt % and more preferably from 35 to 95 wt % with respect to the total amount of the catalyst liquid.

The plating catalyst liquid of the invention containing the foregoing ingredients is less flammable and highly safe. The highly safe catalyst liquid as used herein refers to one which has a flash point of at least 40° C. and a fire point of at least 60° C. at 1 atm and which contains the combustible liquid in an amount of up to 40 wt % with respect to the total amount of the catalyst liquid.

The flash point of the plating catalyst liquid of the invention refers to a value of measurement obtained by the Tag closed cup method according to JIS-K2265.

The plating catalyst liquid of the invention preferably has a fire point of at least 60° C. The fire point is the lowest temperature at which a combustible liquid or solid continues to burn when a small flame is moved closer thereto. The fire point is usually higher by at least 20° C. than the flash point.

The fire point can be determined by the measurement according to the Tag closed cup method (JIS-K2265).

[Acid]

The plating catalyst liquid of the invention further contains an acid. By incorporating an acid in the plating catalyst liquid, the solubility of the palladium compound in the liquid is further improved and the storage stability is also dramatically improved.

Examples of the acid include nitric acid, hydrochloric acid, sulfuric acid, acetic acid and citric acid. Of these, nitric acid, hydrochloric acid and sulfuric acid are preferred in terms of more excellent solubility of the palladium compound and more excellent stability of the liquid. These acids may be used alone or in combination of two or more.

The content of the acid in the plating catalyst liquid of the invention is preferably from 1 to 40 wt % and more preferably from 10 to 25 wt % with respect to the total amount of the catalyst liquid. At too high a content, deposits may not be uniformly formed by plating. At too low a content, adverse effects of the acid, that is, problems such as unimproved solubility and poor stability of the liquid may occur.

The plating catalyst liquid described above may contain other additives according to the intended purpose as long as the effects of the invention are not impaired. Exemplary other additives include swelling agents (e.g., organic compounds such as ketones, aldehydes, ethers and ethers), and surfactants (e.g., low-molecular-weight or high-molecular-weight, anionic, cationic, amphoteric or nonionic surfactants). In the case of using an organic compound for the swelling agent, it is preferred to select a compound which does not impair the effects of the invention.

[Plating Target]

The plating target of the plating catalyst liquid of the invention is not particularly limited and is preferably a hydrophobic resin. A specific example of the plating target includes a hydrophobic resin which has a functional group capable of interacting with the plating catalyst or its precursor. The functional group is hereinafter also referred to as “interactive group.” The specific shape of the hydrophobic resin serving as the plating target is not particularly limited and an optimal shape is suitably selected according to the intended purpose. A plate or a film made of an interactive group-containing hydrophobic resin may be used. Alternatively, a substrate to which an interactive group-containing hydrophobic resin is applied may be used.

The hydrophobic resin is not particularly limited as long as it has low affinity for water and repels water. Examples of the hydrophobic resin include polyimide resins, epoxy resins, acrylic resins, liquid crystal polymers, polycarbonates, ABS, polypropylenes and polytetrafluoroethylenes.

The interactive group is a functional group capable of interacting with the plating catalyst or its precursor, more specifically palladium metal or palladium ion derived from the palladium compound.

The interactive group is preferably a non-dissociative functional group. The non-dissociative functional group refers to a functional group in which no proton is generated by dissociation. The functional group has the function of interacting the plating catalyst or its precursor but does not have high water absorbability or high hydrophilicity unlike the dissociative polar group (hydrophilic group). Therefore, a hydrophobic film which has high resistance to permeation of an alkaline developer can be formed from a polymer having the functional group.

More specifically, the interactive group is preferably selected from among a group capable of forming a coordination bond with a metal ion, a nitrogen-containing functional group, a sulfur-containing functional group and an oxygen-containing functional group. More specific examples thereof include nitrogen-containing functional groups such as imide group, pyridine group, tertiary amino group, ammonium group, pyrrolidone group, amidino group, triazine ring, triazole ring, benzotriazole group, benzimidazole group, quinoline group, pyrimidine group, pyrazine group, nazoline group, quinoxaline group, purine group, triazine group, piperidine group, piperazine group, pyrrolidine group, pyrazole group, aniline group, alkylamine group structure-containing group, isocyanuric structure-containing group, nitro group, nitroso group, azo group, diazo group, azide group, cyano group, and cyanate group (R—O—CN); oxygen-containing functional groups such as phenolic hydroxyl group, hydroxyl group, carbonate group, ether group, carbonyl group, ester group, N-oxide structure-containing group, S-oxide structure-containing group and N-hydroxy structure-containing group; sulfur-containing functional groups such as thiophene group, thiol group, thiocyanuric acid group, benzothiazole group, mercaptotriazine group, thioether group, thioxy group, sulfoxide group, sulfone group, sulfite group, sulfoximine structure-containing group, sulfoxinium salt structure-containing group and sulfonic ester structure-containing group; phosphorus-containing functional groups such as phosphate group, phosphoramide group and phosphine group; groups containing halogen atoms such as chlorine and bromine; and unsaturated ethylene group. In an embodiment showing no dissociation because of the relation with the neighboring atom or atom group, imidazole group, urea group or thiourea group may be used.

Of these, ether group (more specifically a structure represented by —O—(CH₂)_(n)—O— (n is an integer of 1 to 5)) or cyano group is particularly preferred and cyano group is more preferred in terms of high polarity and high adsorptivity on a plating catalyst or its precursor.

In addition, a compound capable of forming a complex such as an inclusion compound, cyclodextrin or crown ether may be applied instead of the functional groups.

The interactive group is more preferably an alkylcyano group. The aromatic cyano group withdraws the electron from the aromatic ring and the unpaired electron donating ability which is important for the adsorption onto the plating catalyst or its precursor is rather low, whereas the alkylcyano group is not attached to the aromatic ring and is therefore preferred in terms of the adsorption onto the plating catalyst or its precursor.

The weight-average molecular weight (Mw) of the interactive group-containing hydrophobic resin is not particularly limited and is preferably from 1,000 to 700,000 and more preferably from 2,000 to 300,000. It is particularly preferred for the weight-average molecular weight to be at least 20,000 in terms of the polymerization sensitivity.

The degree of polymerization is preferably 10 or more and more preferably 20 or more, but is preferably up to 7,000, more preferably up to 3,000, even more preferably up to 2,000 and most preferably up to 1,000.

[Photosensitive Resin Composition]

A preferred example of the interactive group-containing hydrophobic resin of the invention includes a cured product of a photosensitive resin composition which contains a polymer having a functional group capable of interacting with the plating catalyst or its precursor and a polymerizable group.

The cured product of the photosensitive resin composition is obtained by curing the photosensitive resin composition under exposure to energy rays such as UV rays and electron rays. Curing may be performed by a common method under exposure to energy rays such as UV rays. For example, in the case of exposure to UV rays, UV light generators such as a low-pressure mercury vapor lamp, a high-pressure mercury vapor lamp, a ultrahigh pressure mercury lamp, a xenon lamp and a UV-emitting laser (excimer lamp) may be used. Specific conditions include those of exposure performed in the exposure step in the method for producing a laminate having a metal film to be described later.

In cases where the photosensitive resin composition contains a solvent as will be described later, a desired cured product is obtained by a method which involves applying the photosensitive resin composition to a substrate to form a film, optionally removing the solvent in a step provided for drying and irradiating the film with the energy rays as described above. The substrate that is preferably used is one which has the function of forming a direct chemical bond with a polymer having a functional group capable of interacting with the plating catalyst or its precursor and a polymerizable group.

The ingredients contained in the photosensitive resin composition are described below in detail.

[Polymer Having Functional Group Capable of Interacting with Plating Catalyst or its Precursor and Polymerizable Group]

The photosensitive resin composition contains a polymer having a functional group capable of interacting with the plating catalyst or its precursor and a polymerizable group. The functional group and the polymer are hereinafter also referred to as “interactive group” and “specific polymerizable polymer”, respectively. Inclusion of the polymerizable group enables the formation of a bond between polymers and a bond between a polymer and a substrate (graft polymerization).

The interactive group is a functional group capable of interacting with the plating catalyst or its precursor, more specifically palladium metal or palladium ion derived from the palladium compound. The interactive group is as defined above for the hydrophobic resin and the preferable range is also the same.

The polymerizable group the specific polymerizable compound has is a functional group capable of bonding polymers each having a polymerizable group and an interactive group or bonding a polymer having a polymerizable group and an interactive group with a substrate to be described later. Specific examples thereof include vinyl group, vinyloxy group, allyl group, acryloyl group, methacryloyl group, oxetane group, epoxy group, isocyanate group, an active hydrogen-containing functional group and an active group in an azo compound.

The specific polymerizable polymer that may be used in the invention is preferably a polymer obtained by introducing an ethylenically addition-polymerizable unsaturated group (polymerizable group) such as vinyl group, allyl group or (meth)acryl group in a homopolymer or copolymer obtained using an interactive group-containing monomer. The polymer having a polymerizable group and an interactive group has the polymerizable group at least at the end of the main chain or on the side chain and preferably on the side chain.

When one or both of acryl and methacryl are denoted in the specification, acryl and methacryl may be collectively written as “(meth)acryl.”

Monomers other than the interactive group-containing monomer may be used in the formation of the specific polymerizable polymer to reduce the water absorbability and improve the hydrophobicity. Examples of the monomer used with the interactive group-containing monomer include general polymerizable monomers such as diene monomer and acrylic monomer. Of these, unsubstituted alkyl acrylate monomers are preferred. More specifically, tert-butyl acrylate, 2-ethylhexyl acrylate, butyl acrylate, cyclohexyl acrylate and benzyl methacrylate can be preferably used.

The specific polymerizable polymer preferably contains the recurring unit derived from the interactive group-containing monomer in an amount of 30 to 90 mol % and more preferably 40 to 80 mol % with respect to all the recurring units (100 mol %) of the polymer in terms of the interaction formed with the plating catalyst or its precursor.

The weight-average molecular weight (Mw) of the specific polymerizable polymer is not particularly limited and is preferably from 1,000 to 700,000 and more preferably from 2,000 to 300,000. It is particularly preferred for the weight-average molecular weight to be at least 20,000 in terms of the polymerization sensitivity.

The degree of polymerization is preferably 10 or more and more preferably 20 or more, but is preferably up to 7,000, more preferably up to 3,000, even more preferably up to 2,000 and most preferably up to 1,000.

In the practice of the invention, a preferred example of the specific polymerizable polymer includes a copolymer containing recurring units represented by general formulas (1) and (2). This polymer is hereinafter also referred to as “cyano group-containing polymerizable polymer.”

(In general formula (1), R¹ to R⁴ are each independently a hydrogen atom or an optionally substituted alkyl group, Z and Y are each independently a single bond or an optionally substituted divalent organic group, and L¹ is an optionally substituted divalent organic group, and in general formula (2), R⁵ is a hydrogen atom or an optionally substituted alkyl group, X is a single bond or an optionally substituted divalent organic group, and L² is an optionally substituted divalent organic group.)

R¹ to R⁴ in general formula (1) and R⁵ in general formula (2) are each a hydrogen atom or an optionally substituted alkyl group. Examples of the unsubstituted alkyl group include methyl group, ethyl group, propyl group and butyl group. Examples of the substituted alkyl group include methyl group, ethyl group, propyl group and butyl group substituted with methoxy group, hydroxy group, chlorine atom, bromine atom or fluorine atom.

R¹ is preferably a hydrogen atom or a methyl group optionally substituted with a hydroxy group or a bromine atom.

R² is preferably a hydrogen atom or a methyl group optionally substituted with a hydroxy group or a bromine atom.

R³ is preferably a hydrogen atom.

R⁴ is preferably a hydrogen atom.

R⁵ is preferably a hydrogen atom, or a methyl group optionally substituted with a hydroxy group or a bromine atom.

Y and Z in general formula (1) and X in general formula (2) are each a single bond or an optionally substituted divalent organic group. Examples of the divalent organic group include an optionally substituted aliphatic hydrocarbon group, an optionally substituted aromatic hydrocarbon group, an ester group, an amide group, an ether group and combination groups thereof.

Preferred examples of the optionally substituted aliphatic hydrocarbon group include methylene group, ethylene group, propylene group and butylene group optionally substituted with methoxy group, hydroxy group, chlorine atom, bromine atom or fluorine atom.

Preferred examples of the optionally substituted aromatic hydrocarbon group include phenyl group optionally substituted with methoxy group, hydroxy group, chlorine atom, bromine atom or fluorine atom. Of these, —(CH₂)_(n)— where n is an integer of 1 to 3 is preferred and —CH₂— is more preferred.

In general formula (1), L¹ is an optionally substituted divalent organic group. The organic groups represented by L¹ are the same as the organic groups represented by Y and Z in general formula (1).

L¹ is preferably a divalent organic group having a urethane bond or a urea bond and more preferably a divalent organic group having a urethane bond. L¹ even more preferably contains in total 1 to 9 carbon atoms. The total number of carbon atoms in L¹ refers to the total number of carbon atoms included in the optionally substituted divalent organic group represented by L¹.

More specifically, L¹ preferably has a structure represented by general formula (1-1) or (1-2).

In general formulas (1-1) and (1-2), R^(a) and R^(b) are each independently a divalent organic group formed with at least two atoms selected from the group consisting of carbon atom, hydrogen atom and oxygen atom. Preferred examples thereof include optionally substituted methylene, ethylene, propylene and butylene groups, ethylene oxide group, diethylene oxide group, triethylene oxide group, tetraethylene oxide group, dipropylene oxide group, tripropylene oxide group, and tetrapropylene oxide group.

In general formula (2), L² is an optionally substituted divalent organic group. The organic groups represented by L² are the same as the organic groups represented by X in general formula (2).

In particular, L² is preferably a linear, branched or cyclic alkylene group, an aromatic group, or a combination group thereof. The alkylene group may be further combined with the aromatic group via an ether group, an ester group, an amide group, a urethane group or a urea group. Of these, L² preferably contains in total 1 to 15 carbon atoms and is most preferably unsubstituted. The total number of carbon atoms in L² refers to the total number of carbon atoms included in the optionally substituted divalent organic group represented by L².

Specific examples thereof include methylene group, ethylene group, propylene group, butylene group and phenylene group which may be optionally substituted with methoxy group, hydroxy group, chlorine atom, bromine atom or fluorine atom, and combination groups thereof.

In the cyano group-containing polymerizable monomer of the invention, the recurring unit represented by general formula (1) is preferably a recurring unit represented by general formula (3):

wherein R² and R² are each independently a hydrogen atom or an optionally substituted alkyl group, Z is a single bond or an optionally substituted divalent organic group, W is an oxygen atom or NR (where R is a hydrogen atom or an alkyl group and preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 5 carbon atoms), and L² is an optionally substituted divalent organic group.

R¹ and R² in general formula (3) are as defined above for R¹ and R² in general formula (1) and the preferred examples are also the same.

Z in general formula (3) is as defined above for Z in general formula (1) and the preferred examples are also the same. L¹ in general formula (3) is as defined above for L¹ in general formula (1) and the preferred examples are also the same.

In the cyano group-containing polymerizable polymer of the invention, the recurring unit represented by general formula (3) is preferably a recurring unit represented by general formula (4):

wherein R¹ and R² are each independently a hydrogen atom or an optionally substituted alkyl group. V and W are each independently an oxygen atom or NR (where R is a hydrogen atom or an alkyl group and preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 5 carbon atoms), and L¹ is an optionally substituted divalent organic group.

R¹ and R² in general formula (4) are as defined above for R¹ and R² in general formula (1) and the preferred examples are also the same. L¹ in general formula (4) is as defined above for L¹ in general formula (1) and the preferred examples are also the same.

In general formulas (3) and (4), W is preferably an oxygen atom.

In formulas (3) and (4), L¹ is preferably an unsubstituted alkylene group or a divalent organic group having a urethane bond or a urea bond, more preferably a divalent organic group having a urethane bond, and most preferably contains in total 1 to 9 carbons.

In the cyano group-containing polymerizable polymer of the invention, the recurring unit represented by general formula (2) is preferably a recurring unit represented by general formula (5):

wherein R⁵ is a hydrogen atom or an optionally substituted alkyl group, U is an oxygen atom or NR′ (where R′ is a hydrogen atom or an alkyl group and preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 5 carbon atoms), and L² is an optionally substituted divalent organic group.

R⁵ in general formula (5) is as defined for R¹ and R² in general formula (1) and is preferably a hydrogen atom.

L² in general formula (5) is as defined for L² in general formula (2) and is preferably a linear, branched or cyclic alkylene group, an aromatic group, or a combination group thereof.

Particularly in general formula (5), an embodiment in which the linkage moiety of L² with the cyano group is a divalent organic group having a linear, branched or cyclic alkylene group is preferred and an embodiment in which the divalent organic group contains in total 1 to 10 carbon atoms is more preferred.

In another preferred embodiment, the linkage moiety of L² with the cyano group in general formula (5) is a divalent organic group having an aromatic group and the divalent organic group more preferably contains in total 6 to 15 carbon atoms.

The type of polymerization reaction in the synthesis of the cyano group-containing polymerizable polymer according to the invention is not particularly limited. Examples thereof include radical polymerization, cationic polymerization and anionic polymerization. Radical polymerization and cationic polymerization are preferably used in terms of the reaction control. The synthesis method is described in detail in paragraphs [0196] to [0243] of WO 2008-050715.

In the foregoing cyano group-containing polymerizable polymer, the ratio of the polymerizable group-containing recurring unit and that of the cyano group-containing recurring unit with respect to the whole of the copolymer ingredients are preferably within the following ranges.

More specifically, the content of the polymerizable group-containing recurring unit is preferably from 5 to 50 mol % and more preferably from 5 to 40 mol % with respect to the whole of the copolymer ingredients (100 mol %). At too low a content, the reactivity (curing properties, polymerizability) may be reduced, whereas at too high a content, gelation is more likely to occur and may often hinder the synthesis.

The content of the cyano group-containing recurring unit is preferably from 5 to 95 mol %, more preferably from 10 to 95 mol % and even more preferably from 50 to 95 mol % with respect to the whole of the copolymer ingredients (100 mol %) in terms of the adsorption of the plating catalyst.

The weight-average molecular weight (Mw) of the cyano group-containing polymerizable polymer is not particularly limited and is preferably from 1,000 to 700,000 and more preferably from 2,000 to 200,000. It is particularly preferred for the weight-average molecular weight to be at least 20,000 in terms of the polymerization sensitivity.

The degree of polymerization of the cyano group-containing polymerizable polymer is preferably 10 or more and more preferably 20 or more but is preferably up to 7,000, more preferably up to 3,000, even more preferably up to 2,000 and most preferably up to 1,000.

Specific examples of the cyano group-containing polymerizable polymer include those described in paragraphs [0246] to [0252] of WO 2008-050715.

The above-described specific polymerizable polymer such as the cyano group-containing polymerizable polymer may contain a polar group as long as the effects of the invention are not impaired.

The content of the specific polymerizable polymer in the photosensitive resin composition is not particularly limited and is preferably from 2 to 50 wt % and more preferably from 5 to 20 wt % with respect to the total amount of the composition in terms of the ease of handling.

[Solvent]

The photosensitive resin composition may contain a solvent.

The solvent is not particularly limited as long as the above-described specific polymerizable polymer which is the main ingredient of the composition is soluble therein.

Examples of the solvent include alcoholic solvents such as methanol, ethanol, propanol, ethylene glycol, glycerol and propylene glycol monomethyl ether; acids such as acetic acid; ketone solvents such as acetone, methyl ethyl ketone and cyclohexanone; amide solvents such as formamide, dimethylacetamide and N-methylpyrrolidone; nitrile solvents such as acetonitrile and propionitrile; ester solvents such as methyl acetate and ethyl acetate; and carbonate solvents such as dimethyl carbonate and diethyl carbonate.

Particularly in cases where the above-described cyano group-containing polymerizable polymer is used as the specific polymerizable polymer, amide solvents, ketone solvents, nitrile solvents and carbonate solvents are preferred, and more specifically acetone, dimethylacetamide, methyl ethyl ketone, cyclohexanone, acetonitrile, propionitrile, N-methylpyrrolidone and dimethyl carbonate are preferred.

In the case of applying the photosensitive resin composition, the solvent preferably has a boiling point of 50 to 150° C. in terms of the ease of handling. These solvents may be used alone or in combination of two or more.

In cases where the photosensitive resin composition is applied to the substrate, a solvent having a ratio of solvent absorption into the substrate, or the polymerization initiation layer or adhesion promoting layer on the substrate of 5 to 25% may be selected. The ratio of solvent absorption can be determined from the weight change of the substrate or the substrate having the polymerization initiation layer which was pulled up 1,000 minutes after the immersion in a solvent.

In cases where the photosensitive resin composition is applied to the substrate, a solvent having a substrate swelling ratio of 10 to 45% may also be selected. The swelling ratio can be determined from the thickness change of the substrate or the substrate having the polymerization initiation layer or the adhesion promoting layer which was pulled up 1,000 minutes after the immersion in a solvent.

[Additives]

The photosensitive resin composition may optionally contain various additives. Exemplary additives include a surfactant, a plasticizer, a polymerization inhibitor, a rubber ingredient, a flame retardant, a diluent, a thixotropic agent, a pigment, an antifoaming agent, a leveling agent, and a coupling agent. More specifically, surfactants, plasticizers and polymerization inhibitors described in paragraphs [0125] to [0127] of WO 2008-050715 may be used.

[Plating Method]

Next, the plating method using the above-described plating catalyst liquid is described. The plating method of the invention is not particularly limited but a plating method including the following steps is preferred:

-   (1) a catalyst applying step for applying the plating catalyst or     its precursor to a plating target by contacting the above-described     plating catalyst liquid with the plating target; and -   (2) a plating step for plating the plating target obtained in the     catalyst applying step.

Each step is described in detail below.

[Catalyst Applying Step]

The catalyst applying step is a step in which the foregoing plating catalyst liquid is contacted with the plating target to apply palladium (plating catalyst) or palladium ion (precursor) derived from the palladium compound to the plating target. As a result of this step, the plating catalyst liquid permeates the plating target and the plating catalyst or its precursor which serves as the nucleus in the plating treatment is applied (adsorbed) to the plating target.

As described above, a liquid containing a palladium compound, water and a water-soluble combustible liquid serving as the combustible liquid ingredient is used as the plating catalyst liquid. As described above, the plating target which is preferably used is made of an interactive group-containing hydrophobic resin (and is preferably in the form of a substrate) or is a laminate having a substrate and a layer made of an interactive group-containing hydrophobic resin.

Use of the plating catalyst liquid of the invention to treat the hydrophobic plating target (interactive group-containing hydrophobic resin) further facilitates the control of the amount of deposition of palladium serving as the plating catalyst.

In other words, in the case of a conventional plating catalyst liquid containing a non-aqueous solvent, the permeability of the plating catalyst liquid to the hydrophobic plating target and the degree of application of the plating catalyst were too high and the amount of deposition was difficult to control. Consequently, the plating catalyst was deposited on a region of the plating target where the plating catalyst should not be essentially deposited. In a process which involves forming a metal film (e.g., power supply layer) by electroless plating using the plating catalyst and thereafter etching unnecessary portions of the metal film for metalization, more plating catalyst than necessary may be applied because of the difficulty in removing the metal residues including the plating catalyst from the plating target and the conventional plating catalyst liquid was not preferred in terms of the application to electronic components.

On the other hand, in the case of the plating catalyst liquid of the invention, the plating catalyst slowly permeates the hydrophobic plating target and therefore the amount of deposition is easy to control, and the plating catalyst can be deposited to a desired amount by controlling, for example, the contact time between the plating catalyst liquid and the plating target. The plating catalyst of the invention is applied (adsorbed) slowly to the plating target which has no functional group capable of interacting with the plating catalyst or its precursor. Therefore, significantly good pattern plating can be performed in a plating target including an area having no functional group capable of interacting with the plating catalyst or its precursor and an area having a functional group capable of interacting with the plating catalyst or its precursor.

In addition, the catalyst liquid contains water and therefore cannot permeate the interior of the plating target quickly but be efficiently adsorbed to a surface layer area of the plating target with a thickness of several tens of nanometers. In this way, metal residues including the plating catalyst can be easily removed from the plating target in the semi-additive process.

The process of contacting the plating catalyst liquid with the plating target is not particularly limited and exemplary processes include one in which the plating catalyst liquid is applied to the surface of the plating target and one in which the plating target is immersed in the plating catalyst liquid.

In cases where a cured film of the foregoing photosensitive resin composition is formed as desired on each surface of the substrate, the immersion process is preferably used to simultaneously contact the cured layers present on both sides with the plating catalyst liquid. In the immersion, the plating target is preferably immersed in the plating catalyst liquid as it is stirred or shaken in order to keep the concentration of the catalyst near the surface of the plating target in contact with the catalyst.

In cases where the cured product of the photosensitive resin composition including the interactive group-containing specific polymerizable polymer is used, the plating catalyst (palladium) can be efficiently adsorbed onto the interactive group (e.g., cyano group) included in the cured product by means of the interaction based on the intermolecular force such as van der Waals force or the interaction based on the coordination bond using lone-pair electrons.

As for the contact time between the plating catalyst liquid and the plating target, optimal conditions are selected as appropriate for the type of the plating target used and the materials of the plating catalyst liquid. The contact time is preferably from about 30 seconds to about 1 hour and more preferably from about 1 minute to about 30 minutes in terms of the productivity and workability.

As described above, use of the plating catalyst of the invention enables the deposition of extra plating catalyst into the plating target to be suppressed. More specifically, the amount of palladium (plating catalyst) deposited (adsorbed) into the plating target is preferably from 1 to 100 mg/m², more preferably from 5 to 50 mg/m² and even more preferably from 5 to 30 mg/m². When the amount of deposition is too large, the insulation performance may be reduced in cases where the plating target is used for a printed circuit board, or it may be difficult to remove catalyst metal upon formation of interconnects using metal etching according to the subtractive process or semi-additive process. When the amount of deposition is too small, precipitation for forming a film by plating as described below may often not take place well.

The amount of deposition (adsorption) of palladium serving as the plating catalyst can be determined by a process which involves adsorbing the plating catalyst onto a plating target with a certain area, quantifying the palladium concentration by a mass spectrometer (ICP-MS) and dividing the resulting amount of adsorption by the area to measure the amount of deposition in terms of milligram per square meter (mg/m²).

The catalyst applying step may be optionally followed by a step of cleaning the plating target (cleaning step) in order to remove extra plating catalyst deposited onto the plating target.

The solution for use in the cleaning is not particularly limited as long as it does not adversely affect the step to be described below, and a cleaning solution containing water as the main solvent and also containing an organic solvent in an amount of 0.5 to 40 wt % is more preferably used in terms of the removal efficiency.

[Plating Step]

The plating step is a step for plating the plating target obtained in the catalyst applying step. Plating treatment is performed to form a film (metal film) on the plating target. The film formed by plating has excellent electrical conductivity and excellent adhesion to the plating target.

Examples of the type of plating performed in this step include electroless plating and electroplating, and the type may be selected as appropriate for the function of the plating catalyst or its precursor. Of these, electroless plating is preferably performed in terms of improving the formability of a hybrid structure in the plating target and the adhesion. Electroless plating may also be followed by electroplating so that the film obtained by plating may have a desired thickness.

[Electroless Plating]

Electroless plating refers to an operation with which metal is precipitated by a chemical reaction using a solution in which metal ions to be precipitated by plating are dissolved.

Electroless plating in this step is performed by cleaning the plating target having the plating catalyst applied thereto with water to remove extra plating catalyst (metal) and immersing the cleaned plating target in the electroless plating bath. A commonly known electroless plating bath may be used for electroless plating.

In cases where the plating target having the plating catalyst precursor applied thereto is immersed in the electroless plating bath with the plating catalyst precursor adsorbed onto or impregnated in the plating target, the plating target is immersed in the electroless plating bath after the removal of extra precursor (e.g., metal salt) by cleaning with water. In this case, reduction of the plating catalyst precursor and the subsequent electroless plating are performed in the electroless plating bath. A commonly known electroless plating bath may be used for electroless plating.

Reduction of the plating catalyst precursor can also be performed as a separate step preceding electroless plating by preparing a catalyst activating solution (reducing solution) instead of the embodiment using the electroless plating solution as described above. The catalyst activating solution is a solution containing a reducing agent which can reduce the plating catalyst precursor (mainly metal ion) to a zero-valent metal. The concentration of the reducing agent with respect to the total solution is generally in a range of 0.1 wt % to 50 wt % and preferably 1 wt % to 30 wt %. Examples of the reducing agent that may be used include boron reducing agents such as sodium borohydride and dimethylaminoborane, formaldehyde and hypophosphorous acid.

In addition to the solvent, the general composition of the electroless plating bath mainly includes (1) a metal ion for plating, (2) a reducing agent, and (3) an additive for enhancing the stability of the metal ion (stabilizer). In addition to these ingredients, this plating bath may also include known additives such as a stabilizer for the plating bath.

The solvent for use in this plating bath preferably contains an organic solvent which has high affinity for the plating target with low water absorbability and high hydrophobicity. The type and content of organic solvent may be adjusted according to the physical properties of the plating target.

The organic solvent that may be used in the plating bath is preferably a water-soluble solvent, and a water-soluble flammable liquid making up the catalyst liquid of the invention may be used. Examples of the solvent that may be preferably used include ketones such as acetone, and alcohols such as methanol, ethanol, and isopropanol.

Copper, tin, lead, nickel, gold, palladium and rhodium are known metals that may be used in the electroless plating bath. Of these, copper and gold are particularly preferred in terms of the electrical conductivity.

A reducing agent and additives are selected as appropriate for the metal used. For example, the electroless copper plating bath contains a copper salt (CuSO₄), a reducing agent (HCOH) and additives such as a copper ion stabilizer (EDTA), a chelating agent (Rochelle salt) and a trialkanolamine.

The plating bath that may be used in the electroless CoNiP plating contains metal salts (cobalt sulfate and nickel sulfate), a reducing agent (sodium hypophosphite), and a complexing agent such as sodium malonate, sodium malate or sodium succinate.

The electroless palladium plating bath contains a metallic ion ((Pd(NH₃)₄)Cl₂), reducing agents (NH₃, H₂NNH₂) and a stabilizer (EDTA).

These plating baths may contain ingredients other than the above.

Commercial products may be used for the plating liquid as exemplified by THRU-CUP PGT available from C. Uyemura & Co., Ltd., and ATS Addcopper IW available from Okuno Chemical Industries Co., Ltd.

The thickness of the film formed by electroless plating may be controlled by adjusting the metal ion concentration in the plating bath, the immersion time in the plating bath, and the temperature of the plating bath. The film thickness is preferably at least 0.1 μm and more preferably 0.1 to 1 μm in terms of the electrical conductivity. However, in cases where the film formed by electroless plating is used as the electrical conduction layer (power supply layer) to perform electroplating to be described below, a film with a thickness of at least 0.1 μm should be formed uniformly.

The time of immersion in the plating bath is preferably from about 1 minute to about 6 hours and more preferably from about 1 minute to about 3 hours.

The cross-sectional surface of the film obtained as above by electroless plating is observed by a scanning electron microscope (SEM) and it is confirmed that the plating catalyst and the plating metal microparticles are dispersed at a high density in the plating target and particularly in the vicinity of its surface and the metal is further deposited on the plating target. Since the interface between the plating target and the film formed by plating is in a hybrid state of the plating target and the microparticles, good adhesion is achieved even when the interface between the plating target (organic ingredient) and the inorganic substance (catalyst metal or plating metal) is flat and smooth (for example, a 1 mm²-region has a surface roughness R_(a) of up to 100 nm).

[Electroplating]

In this step, in cases where the plating catalyst or its precursor applied in the catalyst applying step functions as the electrode, the plating target to which the plating catalyst or its precursor is applied can be subjected to electroplating.

The foregoing electroless plating may be followed by electroplating using the film formed by electroless plating as the electrode. In this way, a new film with a desired thickness can be easily formed based on the film which was formed by electroless plating and which has good adhesion to the plating target. The film with a thickness suitable to the intended purpose can be formed by electroplating following electroless plating and therefore the metal film of the invention (film formed by plating) can be advantageously used in various applications.

Any conventionally known method may be used for electroplating. Examples of the metal that may be used in electroplating in this step include copper, chromium, lead, nickel, gold, silver, tin, and zinc. In terms of the electrical conductivity, copper, gold and silver are preferred and copper is more preferred.

The thickness of the film (metal film) obtained by electroplating can be controlled by adjusting the concentration of the metal contained in the plating bath, current density or the like. When used in general electrical wiring, the film preferably has a thickness of at least 0.5 μm and more preferably from 1 μm to 100 μm in terms of the electrical conductivity. However, the thickness of wiring is reduced with decreasing line width of the wiring or with miniaturization in order to maintain the aspect ratio. Therefore, the thickness of the film formed by electroplating is not limited to the above-defined range but may be arbitrarily set.

In the invention, a metal or a metal salt derived from the plating catalyst or its precursor, and/or a metal deposited in the plating target by electroless plating is formed in the plating target as a fractal microstructure, whereby the adhesion between the film formed by plating and the plating target can be further improved.

The ratio of metal in the region within a depth from the uppermost surface of the plating target of 0.5 μm is 5 to 50 area % in a cross-sectional image of the plating target taken with a metallograph to determine the amount of metal present in the plating target, and the interface between the plating target and the film formed by plating has an arithmetic mean roughness R_(a) (ISO 4288 (1996)) of 0.01 to 0.5 μm. Even in such a flat and smooth interface, strong adhesion is achieved between the plating target and the metal film.

The plating target including a metal film formed thereon by the above steps (film formed by plating) has good adhesion to the metal film and may be used in various applications. Exemplary applications include electromagnetic wave protecting films, coating films, two-layer copper clad laminate (CCL) materials and electric wiring materials.

The film obtained by plating may also be etched in a pattern shape to form a metal pattern.

[Method for Producing Laminate Having Metal Film]

Next, the method for producing a laminate having a metal film using the foregoing plating catalyst liquid is described. The method for producing the laminate having the metal film according to the invention is not particularly limited but a production method mainly including:

-   (1) a layer-forming step in which a photosensitive resin composition     containing a polymer having a functional group capable of     interacting with a plating catalyst or its precursor and a     polymerizable group is used to form a photosensitive resin     composition layer on a substrate; -   (2) an exposure step in which the photosensitive resin composition     layer is exposed in a pattern shape to form a cured layer in the     exposed area; -   (3) a development step in which part of the photosensitive resin     composition layer unexposed in the exposure step is removed; -   (4) a catalyst applying step in which the patterned cured layer     obtained in the development step is contacted with the foregoing     plating catalyst liquid to apply the plating catalyst or its     precursor to the cured layer; and -   (5) a plating step in which the cured layer to which the plating     catalyst or its precursor was applied in the catalyst applying step     is plated is preferred.

Each step is described in detail below.

[Layer-Forming Step]

The layer-forming step is a step in which a photosensitive resin composition containing a polymer having a functional group capable of interacting with a plating catalyst or its precursor and a polymerizable group is used to form a photosensitive resin composition layer on a substrate. More specifically, it is a step in which a photosensitive resin composition layer is formed on a substrate by applying a photosensitive resin composition to the substrate or immersing the substrate in the photosensitive resin composition.

The above-described polymers and materials are used for the polymer having a functional group capable of interacting with the plating catalyst or its precursor and a polymerizable group (specific polymerizable polymer) and for the photosensitive resin composition, respectively.

The substrate used is described below.

[Substrate]

The substrate may have the function of forming direct chemical bonding with the specific polymerizable polymer. More specifically, the substrate itself may have such surface properties. Alternatively, an intermediate layer separately formed on the substrate may have such properties.

The substrate that may be used in the invention is preferably a dimensionally stable sheet. Examples thereof include paper; paper laminated with plastic materials such as polyethylene, polypropylene and polystyrene; metal sheets made of, for example, aluminum, zinc and copper; plastic films made of, for example, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, polyimide, epoxy, bismaleimide resin, polyphenylene oxide, liquid crystal polymer, polytetrafluoroethylene, ABS, NBR, acrylic polymer, olefin polymer, and polyester resin; and paper or plastic films on which any of the foregoing metals is laminated or vapor-deposited, epoxy or polyimide films impregnated with glass cloth; and interlayer dielectric films for use in multilayer circuit boards (containing as the ingredient glass filler-containing epoxy or polyimide, polyamide-imide, or liquid crystal polymer). In addition, the substrate used may be made of inorganic materials such as glass and ceramic materials.

These substrates may be prepared by mixing inorganic fillers such as silica in terms of improving the dimensional stability and the physical properties. Of these, a substrate containing a resin selected from among epoxy resin, polyimide resin and liquid crystal polymer is preferred.

In cases where the substrate surface has the function of forming direct chemical bonding with the specific polymerizable polymer, the intermediate layer (adhesion promoting layer) to be described later is not necessary.

A substrate which contains polyimide having a polymerization initiation moiety in the skeleton as described in paragraphs [0028] to [0088] of JP 2005-281350 A may also be used in the invention.

A substrate made of an insulating resin and a substrate having an insulating resin layer formed on the surface thereof may also be used in the invention. Use of such a substrate enables the resulting substrate having a metal film formed thereon to be advantageously employed in semiconductor packages and various electrical circuit boards.

A known insulating resin composition is used to obtain a substrate or a film made of the insulating resin. In addition to the resin as the main ingredient, the insulating resin composition may further contain various additives according to the intended purpose. For example, a polyfunctional acrylate monomer is added to enhance the strength of the insulating layer, inorganic or organic particles are added to enhance the strength of the insulating layer and improve the electrical properties, and other means can be applied.

The “insulating resin” as used in the invention refers to a resin having sufficient insulating properties to enable the use in known insulating films and insulating layer, and may be applied to the invention even if it is not a complete insulator as long as it has the insulating properties suitable to the purpose.

Specific examples of the insulating resin include a thermosetting resin, a thermoplastic resin and a mixture thereof. For example, epoxy resin, phenol resin, polyimide resin, polyester resin, bismaleimide resin, polyolefin resin, isocyanate resin, phenoxy resin, polyethersulfone, polysulfone, polyphenylene sulfone, polyphenylene sulfide, polyphenyl ether and polyetherimide as described in paragraphs [0014] to [0019] of JP 2007-144820 A may be used. The insulating resins described in paragraphs [0066] to [0073] of WO 2008-050715 may also be used.

Taking into account the application to semiconductor packages and various electrical circuit boards, the substrate preferably has a surface roughness of up to 500 nm, more preferably up to 100 nm, even more preferably up to 50 nm and most preferably up to 20 nm. The lower limit is preferably as small as possible and more preferably 0 nm. The surface roughness of the substrate (the surface roughness of the intermediate layer and the adhesion promoting layer when they are formed), is preferably as small as possible because the electrical loss during the RF power transmission is reduced in cases where the resulting patterned metal material is applied to wiring.

The adhesion promoting layer to be described below may also be formed on the substrate to improve the adhesion between the substrate and the cured layer of the photosensitive resin composition.

[Adhesion Promoting Layer]

Resin compositions having good adhesion to the substrate and active species (compounds) which may generate active points capable of interacting with the resin film formed of the photosensitive resin composition are preferably used to form the adhesion promoting layer. In cases where the resin making up the resin composition has a moiety where an active point capable of interacting with the resin film having metal ion adsorptivity is generated, it is not necessary to separately add the active species (compounds).

In cases where the substrate is made of a known insulating resin having been used as a material of a multilayer laminate, a build-up substrate, or a flexible substrate, the insulating resin composition (e.g., insulating resin) is preferably used for the adhesion promoting layer in terms of the adhesion to the substrate.

The insulating resin composition for use in forming the adhesion promoting layer may contain the same or different resin as or from the electrical insulating resin making up the substrate. It is particularly preferred to use a resin whose thermophysical properties such as glass transition point, modulus of elasticity and coefficient of linear expansion are close to those of the resin making up the substrate. More specifically, it is preferred to use, for example, the same type of insulating resin as that making up the substrate in terms of the adhesion.

In addition to this ingredient, inorganic or organic particles may be added to enhance the strength of the adhesion promoting layer and improve the electrical properties.

The insulating resin for use in the adhesion promoting layer refers to a resin having sufficient insulating properties to enable the use in known insulating films, and may be applied to the invention even if it is not a complete insulator as long as it has the insulating properties suitable to the purpose.

Specific examples of the insulating resin include a themosetting resin, a thermoplastic resin and a mixture thereof. Examples of the thermoplastic resin include epoxy resin, phenol resin, polyimide resin, polyester resin, bismaleimide resin, polyolefin resin, and isocyanate resin.

Examples of the thermoplastic resin include phenoxy resin, polyethersulfone, polysulfone, polyphenylene sulfone, polyphenylene sulfide, polyphenyl ether and polyetherimide.

A resin having a skeleton which may generate active points where the resin may form an interaction with the photosensitive resin composition may also be used as the insulating resin for use in the adhesion promoting layer. For example, polyimides having a polymerization initiation moiety in the skeleton as described in paragraphs [0018] to [0078] of JP 2005-307140 A are used.

Various compounds may be added to the composition of the adhesion promoting layer according to the intended purpose as long as the effects of the invention are not impaired.

Specific examples include substances capable of reducing the stress during heating such as rubber and SBR latex, a binder for improving the film properties, a plasticizer, a surfactant, and a viscosity modifier.

Composite materials of the resins and other ingredients may also be used for the adhesion promoting layer in order to enhance the properties of the resin film such as mechanical strength, heat resistance, weather resistance, flame resistance, water resistance, and electrical characteristics. Exemplary materials that may be used to obtain the composite materials include paper, glass fiber, silica particles, phenol resin, polyimide resin, bismaleimide triazine resin, fluororesin and polyphenylene oxide resin.

In addition, the adhesion promoting layer may optionally include at least one filler used in a common resin material for circuit boards. The filler is selected from among, for example, inorganic fillers such as silica, alumina, clay, talc, aluminum hydroxide and calcium carbonate and organic fillers such as cured epoxy resin, cross-linked benzoguanamine resin and cross-linked acrylic polymer. Of these, silica is preferably used as the filler.

The adhesion promoting layer may optionally further include at least one of various additives such as colorant, flame retardant, adhesion promoter, silane coupling agent, antioxidant and UV absorber.

Each of these materials is preferably added in a range of 0 to 200 wt % and more preferably 0 to 80 wt % with respect to the resin which is the main ingredient. In cases where the adhesion promoting layer and its adjoining substrate show physical values identical to or close to each other under the action of heat or electricity, the additives may not be added. In cases where the additives are used in amounts exceeding 200 wt % with respect to the resin, there is concern that the properties such as the strength the resin itself essentially has may be reduced.

As described above, the active species (compounds) which may generate active points capable of interacting with the photosensitive resin composition are preferably used for the adhesion promoting layer. Any kind of energy may be applied to generate the active points and light (UV rays, visual rays and X-rays), plasma (oxygen, nitrogen, carbon dioxide and argon), heat and electricity are preferably used. In addition, the surface may be chemically decomposed by an oxidizing liquid (potassium permanganate solution) to generate the active points.

Exemplary active species include polymerization initiators such as a thermal polymerization initiator and a photopolymerization initiator. The adhesion promoting layer preferably contains the polymerization initiator in an amount of 0.1 to 50 wt % and more preferably 1.0 to 30 wt % with respect to the total amount of the adhesion promoting layer.

The adhesion promoting layer generally has a thickness of preferably 0.1 to 10 μm and more preferably 0.2 to 5 μm. At a thickness within the above-defined range, the adhesion promoting layer sufficiently adheres to the cured layer of the photosensitive resin composition. The adhesion of the same level as in the case using the adhesive is achieved although the adhesion promoting layer is thinner than the layer using the common adhesive. As a result, a laminate with a smaller total thickness which has a metal film with excellent adhesion can be obtained.

The adhesion promoting layer preferably has a surface roughness R_(z) as measured by the 10-point mean roughness method according to JIS B 0601 (1994) of up to 3 μm and more preferably up to 1 μm in order to improve the physical properties of the film formed by plating (metal film). When the surface roughness R_(z) is within the above-defined range, the adhesion promoting layer is advantageously used to manufacture ultra-fine printed circuit boards including, for example, a circuit pattern with a line width of up to 25 μm and a line-to-line spacing of up to 25 μm.

The adhesion promoting layer is formed on the substrate by layer forming processes such as coating, transfer and printing.

The adhesion promoting layer may be patterned as desired by printing processes such as gravure printing, screen printing, flexographic printing, ink-jet printing or imprinting, or by development such as wet etching, dry etching, ablation, (negative/positive) curing and plasticization by exposure to light.

The adhesion promoting layer formed on the substrate may be subjected to a curing treatment step after applying any energy thereto. Examples of the energy applied include light, heat, pressure and electron rays. In the embodiment under consideration, heat or light is general and in the case of heat, heat is preferably applied at 100 to 300° C. for 5 to 120 minutes.

The conditions for thermal curing vary with the type of the substrate material and the type of the resin composition making up the adhesion promoting layer. The conditions also depend on the curing temperature of these materials and thermal curing is preferably performed at 120 to 220° C. for 20 to 120 minutes.

The curing treatment step may be performed just after the formation of the adhesion promoting layer. Alternatively, the curing treatment step may be performed after all the other steps following the formation of the adhesion promoting layer are performed if a preliminary curing treatment is performed for about 5 to about 10 minutes after the formation of the adhesion promoting layer.

The formation of the adhesion promoting layer may be followed by surface roughening by a dry and/or wet process in order to improve the adhesion to the cured film of the photosensitive resin composition to be formed on its surface. Exemplary dry surface roughening processes include mechanical polishing such as buffing and sandblasting, and plasma etching. On the other hand, wet surface roughening processes include treatments using chemicals including oxidants such as permanganates, bichromates, ozone, hydrogen peroxide/sulfuric acid and nitric acid, strong bases and solvents that may swell resins.

As compared to the cured layer of the photosensitive resin composition to be described later, the plating catalyst or its precursor is less likely to deposit to the adhesion promoting layer. Therefore, there is a large difference in the ease of deposition of the plating catalyst or its precursor between the adhesion promoting layer and the cured layer of the photosensitive resin composition. In other words, the plating catalyst has deposition selectivity. As a result, the plating catalyst mainly deposits to the cured layer of the photosensitive resin composition, which enables better pattern plating to be performed.

(Film-Forming Process)

As described above, the process of forming the photosensitive resin composition layer on the substrate is not particularly limited. Exemplary processes include application of the photosensitive resin composition to the substrate, and immersion of the substrate in the photosensitive resin composition. The application process is preferred because the layer thickness is easily controlled.

The process of applying the photosensitive resin composition to the substrate is not particularly limited and examples thereof include known coating processes such as blade coating, rod coating, squeeze coating, reverse roll coating, transfer roll coating, spin coating, bar coating, air knife coating, gravure printing, and spray coating.

A step of heating the photosensitive resin composition layer may optionally be provided to remove the solvent in the photosensitive resin composition layer after the application. The drying temperature and time are selected as appropriate and the photosensitive resin composition layer is preferably dried at 100 to 200° C. for 10 minutes to 1 hour in terms of the production efficiency and the handling.

The photosensitive resin composition layer obtained by this step has an appropriately selected thickness. The thickness is preferably from 0.1 to 10 μm and more preferably from 0.2 to 5 μm in terms of the application to electronic components such as printed circuit boards.

[Exposure Step]

The exposure step is a step in which the photosensitive resin composition layer obtained in the application step is exposed in a pattern shape to form a cured layer. The exposure treatment causes the crosslinking reaction between the resins to take place in the photosensitive resin composition layer and the covalent bond with the substrate to be formed to obtain the cured film.

The cured layer of the photosensitive resin composition is preferably formed on the substrate by exposure to light using a general means called surface graft polymerization. Graft polymerization is a process in which active species are applied onto a polymer compound chain to further polymerize another monomer which initiates polymerization under the action of the active species to thereby synthesize a graft polymer.

Known processes described in literatures may be used for the surface graft polymerization that may be applied to the invention. For example, surface graft polymerization processes including photografting polymerization and plasma irradiation graft polymerization are described in Shinkobunshi Jikkengaku (New Polymer Experiments) (Vol. 10, Ed. by the Society of Polymer Science, Japan, Kyoritsu Shuppan Co., Ltd., 1994, p. 135). Further, graft polymerization using radiations such as γ-rays and electron beams is described in Kyuchaku Gijutsu Binran (Handbook of Adsorption Technology) (pp. 203 and 695, supervised by Takeuchi, NTS Co., February 1999).

Photografting polymerization is performed by processes specifically described in JP 63-92658 A, JP 10-296895 A and JP 11-119413 A.

The other process than the foregoing surface graft polymerization process that may be applied upon the formation of the cured layer of the photosensitive resin composition is a process which involves applying a reactive functional group such as trialkoxysilyl group, isocyanate group, amino group, hydroxyl group or carboxyl group to the end of a polymer compound chain and bonding by a coupling reaction between the reactive functional group and a functional group present at the surface of the substrate.

Of these processes, in terms of increasing the amount of graft polymer formed, photografting polymerization and particularly UV-photografting polymerization are preferably used to form the cured layer of the photosensitive resin composition in which the specific polymerizable polymer is chemically bonded to the substrate.

For patterning, exposure means using a mask is usually used but scanning exposure using various lasers may also be used.

The exposure light source is appropriately selected and examples thereof include UV lamp, mercury lamp, metal halide lamp, xenon lamp, chemical lamp, and carbon arc lamp. Examples of the radiation include electron rays, X-rays, ion beams and far infrared rays, and g-line rays, i-line rays, deep UV rays, and high-density energy beams (laser beams) may also be used.

Scanning exposure using an infrared laser, high-intensity flash exposure using a xenon discharge lamp and performed via a mask, and exposure using an infrared lamp are particularly preferred.

The exposure time is selected as appropriate for the type of the photosensitive resin composition used and is preferably from 5 seconds to 30 minutes in terms of the workability.

An exposure power of preferably 10 to 5,000 mJ/cm² and more preferably 50 to 3,000 J/cm² is applied to facilitate the progress of the graft reaction with the substrate.

The cured layer obtained by exposure and curing of the photosensitive resin composition layer has no surface roughness due to uneven application and has a very flat and smooth surface. Even the cured layer having such a flat and smooth surface forms a strong and irreversible interaction for coordinate bonding with palladium as the plating catalyst based on the function of the interactive group and therefore can also achieve good adhesion to the metal film formed by plating which is performed using the plating catalyst adsorbed to the cured layer as the starting point.

[Development Step]

The development step is a step in which part of the photosensitive resin composition layer unexposed in the exposure step is removed, that is, the uncured area of the photosensitive resin composition layer is removed by a developer or the like. The uncured area is removed by development to form a patterned cured layer.

The development process is not particularly limited as long as the uncured area of the photosensitive resin composition layer can be removed, and an optimal process is selected as appropriate for the photosensitive resin composition used. An example thereof includes a process using a highly alkaline solution at a pH of 13.0 to 13.8 as the developer. In the case of development using a highly alkaline developer, exemplary processes include a process in which the substrate having an uncured area of the photosensitive resin composition layer as obtained by the exposure step is immersed in the solution, and a process in which the developer is applied onto the substrate, and the immersion process is preferred. In the case of the immersion process, the immersion time is preferably from about 1 minute to about 30 minutes in terms of the productivity and workability.

Another process involves using a solvent in which the photosensitive resin composition is soluble as the developer and immersing the substrate in the solvent.

[Catalyst Applying Step]

The catalyst applying step is a step in which the cured layer obtained in the development step is contacted with the foregoing plating catalyst liquid to apply the plating catalyst or its precursor derived from the palladium compound to the cured layer. As a result of this step, the plating catalyst liquid permeates the cured layer and the palladium or palladium ion which serves as the nucleus in the plating treatment is applied (adsorbed) to the cured layer.

In this step, the same plating catalyst liquid as in the catalyst applying step in the above-described plating method is used and the same method as above is performed. Therefore, the description of this step is omitted.

[Plating Step]

The plating step is a step in which the cured layer to which the plating catalyst or its precursor was applied in the catalyst applying step is plated to form a film (metal film). In other words, the laminate having the metal film can be obtained by further plating the substrate having the cured layer to which the plating catalyst was applied. In the case of obtaining the patterned metal film, a metal film may be formed on the whole surface of the substrate and partially etched, or the cured layer may be preliminarily formed in a pattern shape before being plated.

In this step, electroless plating or electroplating is performed as in the plating step in the foregoing plating method. Electroless plating and electroplating are performed as described above and their description is omitted.

A substrate having a metal film (laminate) can be obtained by these steps. More specifically, the laminate obtained has the substrate, the cured layer of the photosensitive resin composition formed on the substrate, and the metal film formed on the cured layer. The substrate used may be of a laminated structure including the substrate and the adhesion promoting layer formed thereon. A metal film-containing laminate having metal layers formed on both surfaces thereof can be obtained by subjecting the surfaces of the substrate to these steps.

The resulting metal film-containing laminate has a cured layer which is formed on the surface of the substrate and which has good flatness and a metal layer which also has high adhesion strength, and can be therefore used in various applications such as electromagnetic wave protecting films, coating films, two-layer CCL materials and electric wiring materials and in particular advantageously used in applications which must ensure RF transmission because of improved flatness of the interface between the metal film and the cured layer.

In a preferred embodiment of the metal film-containing laminate of the invention, the metal film is preferably formed by plating on a substrate (or a cured layer of the photosensitive resin composition if any) having a surface roughness of up to 500 nm (more preferably up to 100 nm and most preferably 0). The strength of adhesion between the substrate and the metal pattern is preferably at least 0.2 kN/m (and more preferably at least 0.5 kN/m).

The substrate was cut vertically to its surface and the cross sectional surface was observed by SEM to measure the arithmetic mean roughness R_(a) of the substrate according to JIS B0633-2001.

The adhesion is determined by a method which involves adhering a copper sheet with a thickness of 0.1 mm to the surface of the film formed by plating (metal pattern) with an epoxy adhesive Araldite (Ciba-Geigy Ltd.), drying the adhesive at 140° C. for 4 hours and conducting a 90-degree peel test according to JIS C 6481, or a method which involves directly peeling off the end of the film itself formed by plating to conduct a 90-degree peel test according to JIS C 6481.

According to the method for producing the metal film-containing laminate of the invention, a high-definition pattern to which the plating catalyst is selectively deposited with high efficiency is formed and the laminate obtained may have a high-definition metal film pattern having good adhesion to the substrate.

The thus obtained laminate having the metal film is useful to manufacture flexible printed circuit boards used in various applications such as semiconductor chips, various electrical circuit boards, flexible printed circuits (FPC), chips on film (COF), tape automated bonding (TAB), antennas, multilayer circuit boards and mother boards.

EXAMPLES

The present invention is described below more specifically by way of examples. However, the present invention should not be construed as being limited to the following examples. Unless otherwise specified, the weight ratio is expressed by percentage or parts by weight.

(Preparation of Plating Catalyst Liquid)

Any of the water-soluble combustible liquids, palladium acetate (Wako Pure Chemical Industries, Ltd.) and nitric acid (Wako Pure Chemical Industries, Ltd.) were added to water in predetermined amounts and the mixture was stirred at 26° C. for 1 week to achieve saturated dissolution thereby preparing plating catalyst liquids in Examples 1 to 18 as shown in Table 1.

Diethylene glycol diethyl ether (Wako Pure Chemical Industries, Ltd.), diethylene glycol dimethyl ether (Wako Pure Chemical Industries, Ltd.), and triethylene glycol monomethyl ether (Wako Pure Chemical Industries, Ltd.) were used for the water-soluble combustible liquid. Diethylene glycol diethyl ether and diethylene glycol dimethyl ether correspond to water-soluble organic solvents having no hydroxyl group.

TABLE 1 Type Palla- of Solvent Water Acid dium Example solvent content content content acetate Example 1 Tri- 39 60.75 — 0.25 ethyl- wt % wt % wt % Example 2 ene 39 55.75 HNO₃ 5 wt % 0.25 glycol wt % wt % wt % Example 3 mono- 39 50.75 HNO₃ 10 wt % 0.25 methyl wt % wt % wt % Example 4 ether 39 45.75 HNO₃ 15 wt % 0.25 wt % wt % wt % Example 5 39 40.75 HNO₃ 20 wt % 0.25 wt % wt % wt % Example 6 39 35.75 HNO₃ 25 wt % 0.25 wt % wt % wt % Example 7 Di- 39 60.75 — 0.25 ethyl- wt % wt % wt % Example 8 ene 39 55.75 HNO₃ 5 wt % 0.25 glycol wt % wt % wt % Example 9 dim- 39 50.75 HNO₃ 10 wt % 0.25 ethyl wt % wt % wt % Example 10 ether 39 45.75 HNO₃ 15 wt % 0.25 wt % wt % wt % Example 11 39 40.75 HNO₃ 20 wt % 0.25 wt % wt % wt % Example 12 39 35.75 HNO₃ 25 wt % 0.25 wt % wt % wt % Example 13 Di- 39 60.75 — 0.25 ethyl- wt % wt % wt % Example 14 ene 39 55.75 HNO₃ 5 wt % 0.25 glycol wt % wt % wt % Example 15 diethyl 39 50.75 HNO₃ 10 wt % 0.25 ether wt % wt % wt % Example 16 39 45.75 HNO₃ 15 wt % 0.25 wt % wt % wt % Example 17 39 40.75 HNO₃ 20 wt % 0.25 wt % wt % wt % Example 18 39 35.75 HNO₃ 25 wt % 0.25 wt % wt % wt %

The plating catalyst liquids prepared in Examples 1 to 18 were examined for the catalyst solubility and catalyst stability. The results of the respective catalyst liquids are shown in Table 2.

The catalyst solubility in Table 2 was rated “good” when palladium acetate substantially dissolved on day 3 to obtain a transparent solution as a result of visual check on the mixture that was stirred at 26° C. to prepare the plating catalyst liquid. The catalyst solubility was rated “fair” when palladium acetate partially dissolved in a period of more than 3 days but within 1 week, and “poor” when palladium acetate did not dissolve at all in a period exceeding 1 week.

The catalyst stability was rated “poor” when the solution at 25° C. changed into black color within 1 day, “fair” when the solution changed in color in a period of more than 1 day but within 3 days, and “good” when the solution did not change in color in a period exceeding 1 week. It seems that the solution changed into black color due to the modification of the dissolved palladium catalyst.

The flash point of each of the plating catalyst liquids prepared in Examples 1 to 18 was measured by the Tag closed cup method according to JIS-K2265. The results obtained are shown in Table 2. The flash point of “80° C.<” in Table 2 means that the flash point is above 80° C.

TABLE 2 Type of plating catalyst liquid Catalyst solubility Catalyst stability Flash point Example 1 Fair Fair 80° C.< Example 2 Fair Fair 80° C.< Example 3 Good Fair 80° C.< Example 4 Good Fair 80° C.< Example 5 Good Fair 80° C.< Example 6 Good Fair 80° C.< Example 7 Fair Good 77.7° C. Example 8 Fair Good 77.7° C. Example 9 Good Good 77.7° C. Example 10 Good Good 77.7° C. Example 11 Good Good 77.7° C. Example 12 Good Good 77.7° C. Example 13 Fair Good 78.6° C. Example 14 Fair Good 78.6° C. Example 15 Good Good 78.6° C. Example 16 Good Good 78.6° C. Example 17 Good Good 78.6° C. Example 18 Good Good 78.6° C.

Table 2 confirmed that the respective catalyst liquids show good catalyst solubility and good catalyst stability. In particular, the nitric acid-containing plating catalyst liquids (in Examples 3 to 6, 9 to 12 and 15 to 18) showed excellent catalyst solubility. The water-soluble organic solvents containing no hydroxyl group (in Examples 7 to 18) showed excellent catalyst stability.

The respective plating catalyst liquids shown in Table 1 showed a flash point of 40° C. or higher.

[Preparation of Laminate Having Metal Film] [Preparation of Substrate]

A glass epoxy substrate having an interlayer dielectric film GX-13 (ABF available from Ajinomoto Co., Inc.) laminated thereon was prepared. The interlayer dielectric film had a thickness of 40 μm and a surface roughness (R_(z)) of 0.6 μm.

(Formation of Adhesion Promoting Layer 1)

A mixture solution containing 11.9 parts by weight of JER806 (bisphenol F epoxy resin available from Japan Epoxy Resins Co., Ltd.), 4.7 parts by weight of LA7052 (curing agent PHENOLITE available from Dainippon Ink and Chemicals, Inc.), 21.7 parts by weight of YP50-35EK (phenoxy resin available from Tohto Kasei Co., Ltd.), 61.6 parts by weight of cyclohexanone and 0.1 part by weight of 2-ethyl-4-methylimidazole (curing accelerator) was filtered through a filter cloth with a mesh size of 200 to prepare a coating liquid.

The coating liquid was applied onto the interlayer dielectric film by spin coating and then dried at 170° C. for 60 minutes for curing to obtain Substrate A1 having Adhesion promoting layer 1 formed therein. The cured film (intermediate layer) had a thickness of 0.5 μm. The Substrate Al had a surface roughness (R_(a)) of 0.12 μm.

[Cured Layer of Photosensitive Resin Composition] (Synthesis of Polymer A Having Polymerizable Group and Interactive Group]

First of all, Polymer A having a polymerizable group and an interactive group was synthesized as described below. To a three-neck flask with a volume of 500 mL were added 20 mL of ethylene glycol diacetate, 7.43 g of hydroxyethyl acrylate and 32.08 g of cyanoethyl acrylate, and the mixture was heated to 80° C. To the mixture was added dropwise a mixture solution containing 0.737 g of V-601 and 20 mL of ethylene glycol diacetate over 4 hours. After the dropwise addition, the mixture was reacted for 3 hours.

To the reaction solution were added 0.32 g of di-tert-butylhydroquinone, 1.04 g of U-600 (Nitto Kasei Co., Ltd.), 21.87 g of Karenz AOI (Showa Denko K.K.) and 22 g of ethylene glycol diacetate and the mixture was reacted at 55° C. for 6 hours. Then, to the reaction solution was added 4.1 g of methanol and the reaction was allowed to proceed for another 1.5 hours. After the end of the reaction, the solid was collected by reprecipitation with water to obtain the Polymer A which was a specific polymerizable polymer having nitrile group as the interactive group. The ratio between the polymerizable group-containing recurring unit and the nitrile group-containing recurring unit (molar ratio) was 22:78. The molecular weight (Mw) in terms of polystyrene was 82,000 (Mw/Mn=3.4).

(Preparation of Coating Solution)

The Polymer A (10 parts by weight) and acetonitrile (90 parts by weight) were mixed with stirring to prepare a coating solution with a solids content of 10 wt %.

(Film-Forming Step and Exposure Step: Curing of Photosensitive Resin Composition Layer)

The thus prepared coating solution was applied to the resin layer of the Substrate A1 to a thickness of 1 μm by spin coating and dried at 80° C. for 30 minutes. Then, a UV exposing machine (model: UVF-502S, lamp: UXM-501MD) available from San-Ei Electric Co., Ltd. was used to expose the insulating resin layer of the Substrate A1 in a pattern with a line width of 12.5 μm and a line-to-line spacing of 12.5 μm by 660-second irradiation via a mask including a light transmission part made of quartz and a mask part (non-exposed part) to which chromium was vapor-deposited. The irradiation power as measured with an accumulated UV meter UIT 150 and a light receiving sensor UVD-5254 (Ushio Inc.) was 1.5 mW/cm². A patterned cured layer made of the Polymer A was thus formed on the insulating resin layer of the Substrate A1. The amount of accumulated exposure was 500 mJ/cm².

The same amount of exposure was applied to prepare another cured layer of the Polymer A by exposing the whole surface without using a mask.

Thereafter, the substrate having the cured layer formed thereon was immersed in stirred acetonitrile for 5 minutes and then washed with distilled water to thereby obtain Substrate A2 having a patterned cured layer and Substrate A3 having a cured layer formed on its whole surface.

(Measurement of Physical Properties of Cured Layer)

The patterned cured layer on the Substrate A2 and the cured layer on the whole surface of the Substrate A3 were determined for the physical properties according the above-described measurement method. The results of both the layers were as described below.

-   Saturated water absorption at 25° C. and 50% RH: 1.2 wt % -   Saturated water absorption at 25° C. and 95% RH: 3.4 wt %

(Catalyst Applying Step)

The Substrate A2 having the patterned cured layer and the Substrate A3 having the cured layer on the whole surface thereof were immersed for 5 minutes in the plating catalyst liquids prepared in Examples 1 to 18 and were then washed with water. The catalyst was applied to the cured layers and in the case of using the plating catalyst prepared in Example 17, the amount of catalyst applied (palladium deposited) to the Substrates A2 and A3 was 30 mg/m².

(Plating Step: Electroless Plating)

A Thru-Cup PGT (C. Uyemura & Co., Ltd.) and the electroless plating bath of the composition indicated below were used for the Substrate A2 having the patterned cured layer to which the plating catalyst was applied, to thereby perform electroless plating at an electroless plating temperature of 26° C. for 30 minutes. A copper film with a thickness of 0.5 μm was obtained by electroless plating in each sample.

The materials used for the electroless plating solution were as follows:

Distilled water 79.2 wt % PGT-A  9.0 wt % PGT-B  6.0 wt % PGT-C  3.5 wt % Formalin (formaldehyde  2.3 wt % solution from Wako Pure Chemical Industries, Ltd.)

The metal pattern obtained using the Substrate A2 having the patterned cured layer was observed by an optical microscope (color 3D laser scanning microscope VK-9700 (Keyence Corporation) and it was confirmed that a copper pattern with a line width of 13 μm and a line-to-line spacing of 12 μm was formed without defects.

(Evaluation of Surface Roughness)

A cross-sectional image of the interface between the cured layer and the metal film (film formed by plating) was taken by SEM at a magnification of 10,000× and the image was used to measure the arithmetic mean roughness R_(a) (μm) of the interface according to JIS B0633-2001. The results are shown in Table 3 below.

(Evaluation of Adhesion)

The Substrate A3 which has the cured layer formed on the whole surface thereof and which was obtained not by pattern exposure using a mask but by exposure of the whole surface was used to prepare samples for evaluating the adhesion. The Substrate A3 and the plating catalyst liquids in Examples 1 to 18 were used to repeat the same method as above till the electroless plating.

Subsequently, the copper film formed by electroless plating was used as the power supply layer to perform electroplating at 3 A/dm² for 20 minutes in the electroplating bath of the composition indicated below. A copper film with a thickness of 12 μm was obtained by electroplating in each sample.

Composition of electroplating bath

Copper sulfate  38 g Sulfuric acid  95 g Hydrochloric acid  1 mL Copper Gleam PCM (Meltex Inc.)  3 mL Water 500 g

The resulting copper-plated substrate was heated at 170° C. for 1 hour.

The 90° peel strength of the film obtained by plating was determined with a tensile tester RTM-100 (A & D Co., Ltd.) by applying a tensile strength of 10 mm/min to a portion with a width of 5 mm. The results of the respective samples are shown in Table 3.

(Evaluation of Removability of Metal Residues by Etching)

The Substrate A3 which has the cured layer formed on the whole surface thereof and which was obtained not by pattern exposure using a mask but by exposure of the whole surface was used to prepare samples for evaluating the removability of metal residues. The Substrate A3 and the plating catalyst liquids in Examples 1 to 18 were used to repeat the same method as above till the electroless plating. Thereafter, a comb-like pattern described in JPCA BU-01 2007 was formed by a known semi-additive process.

In the process, the electroplating resist was developed and peeled off. Then, flash etching was performed for 30 seconds with an etching solution of sulfuric acid/hydrogen peroxide to remove copper deposited by electroless plating, thereby obtaining a circuit board. Then, the DC insulation resistance between the pads of the comb-like structure was measured by a resistance meter R8340A (ADC Corporation). The resistance value obtained with the plating catalyst liquid in Example 1 was 3.0×10¹¹Ω, which was a good value. Also in cases where the other plating catalyst liquids in Examples 2 to 18 were used, good resistance values of about 3.0×10¹¹Ω were obtained.

On the other hand, a solution of palladium nitrate (0.05 wt %) in acetone was used as the plating catalyst liquid to prepare a circuit board by the same method as above. The resistance value obtained was 2.0×10³Ω. From a practical point of view, the DC insulation resistance value is preferably at least 10¹⁰Ω and the use of the circuit board is limited at a DC insulation resistance value of less than 10⁴Ω. It was confirmed that the circuit board obtained using the plating catalyst liquid of the invention showed good insulation resistance as described above.

TABLE 3 Surface Ad- Plating Plating Patterned rough- hesion catalyst deposition plating Storage ness strength Example liquid used properties properties stability Ra (μm) (kN/m) 1 Example 1  Good Good Fair 0.03 0.7 2 Example 2  Good Good Fair 0.03 0.7 3 Example 3  Good Good Fair 0.03 0.7 4 Example 4  Good Good Fair 0.03 0.7 5 Example 5  Good Good Fair 0.03 0.7 6 Example 6  Good Good Fair 0.03 0.7 7 Example 7  Good Good Fair 0.03 0.7 8 Example 8  Good Good Good 0.03 0.7 9 Example 9  Good Good Good 0.03 0.7 10 Example 10 Good Good Good 0.03 0.7 11 Example 11 Good Good Good 0.03 0.7 12 Example 12 Good Good Good 0.03 0.7 13 Example 13 Good Good Fair 0.03 0.7 14 Example 14 Good Good Good 0.03 0.7 15 Example 15 Good Good Good 0.03 0.7 16 Example 16 Good Good Good 0.03 0.7 17 Example 17 Good Good Good 0.03 0.7 18 Example 18 Good Good Good 0.03 0.7

Table 3 shows the plating deposition properties, which were rated “good” when metal deposits were uniformly formed on the whole surface within 30 minutes by plating under the conditions described in Examples, “fair” when metal deposits were uniformly formed as above in a period of more than 30 minutes but up to 1 hour, and “poor” when no uniform film was formed by plating even in a period exceeding 1 hour.

The patterned plating properties were rated “good” when no deposition was seen in the non-patterned area (area where no patterned cured film was formed) on the Substrate A2 after 2-hour electroless plating, “fair” when no deposition was seen after 30-minute electroless plating but deposition was seen after 2-hour electroless plating, and “poor” when deposition was seen after 30-minute electroless plating.

The storage stability was rated “good” when the film formed by performing the same plating step as above after 1-month storage of the plating catalyst liquids in Examples 1 to 18 at 25° C. had no change in the criteria for evaluating the plating deposition properties and the patterned plating properties, “fair” when one of the plating deposition properties and the patterned plating properties deteriorated, and “poor” when both of the plating deposition properties and the patterned plating properties deteriorated.

From a practical point of view, no sample should be rated “poor” in the foregoing items.

The results in Table 3 confirmed that the various plating catalyst liquids had good plating deposition properties, good patterned plating properties and good storage stability. Particularly Examples 7 to 18 in which a water-soluble organic solvent having no primary or secondary hydroxyl group was used showed excellent storage stability.

Based on the good patterned plating properties, it was confirmed that the plating catalyst was hardly applied to the non-patterned area where no cured layer was formed. In other words, it was shown that the plating catalyst liquid of the invention has good selectivity and controllability in the application of the plating catalyst to the plating target. It was also shown that, when used in the semi-additive process, the plating catalyst of the invention has a high interconnect resistance and can be advantageously used in this process.

In the various plating catalyst liquids, the surface roughness R_(a) of the interface between the cured layer and the metal film (film formed by plating) was also small and the adhesion strength of the metal film was also good. 

1. A plating catalyst liquid comprising: a palladium compound; water; and a water-soluble combustible liquid serving as a combustible liquid ingredient, wherein the catalyst liquid has a flash point of 40° C. or more and contains the water-soluble combustible liquid in an amount of 0.1 to 40 wt %.
 2. The plating catalyst liquid according to claim 1, wherein the water-soluble combustible liquid is a water-soluble organic solvent having no primary or secondary hydroxyl group.
 3. The plating catalyst liquid according to claim 1 which further comprises an acid.
 4. The plating catalyst liquid according to claim 1, wherein a plating target is made of a hydrophobic resin having a functional group capable of interacting with a plating catalyst or its precursor.
 5. The plating catalyst liquid according to claim 4, wherein the hydrophobic resin is a cured product of a photosensitive resin composition containing a polymer which has the functional group capable of interacting with the plating catalyst or its precursor and a polymerizable group.
 6. The plating catalyst liquid according to claim 5, wherein the polymer is a copolymer containing recurring units represented by general formulas (1) and (2):

(in general formula (1), R¹ to R⁴ are each independently a hydrogen atom or an optionally substituted alkyl group, Z and Y are each independently a single bond or an optionally substituted divalent organic group, and L¹ is an optionally substituted divalent organic group, and in general formula (2), R⁵ is a hydrogen atom or an optionally substituted alkyl group, X is a single bond or an optionally substituted divalent organic group, and L² is an optionally substituted divalent organic group).
 7. A plating method comprising: a catalyst applying step for applying a plating catalyst or its precursor to a plating target by contacting the plating catalyst liquid according to claim 1 with the plating target; and a plating step for plating the plating target obtained in the catalyst applying step.
 8. The plating method according to claim 7, wherein the plating target is made of a hydrophobic resin having a functional group capable of interacting with the plating catalyst or its precursor.
 9. The plating method according to claim 8, wherein the hydrophobic resin is a cured product of a photosensitive resin composition containing a polymer which has the functional group capable of interacting with the plating catalyst or its precursor and a polymerizable group.
 10. The plating method according to claim 9, wherein the polymer is a copolymer containing recurring units represented by general formulas (1) and (2):

(in general formula (1), R¹ to R⁴ are each independently a hydrogen atom or an optionally substituted alkyl group, Z and Y are each independently a single bond or an optionally substituted divalent organic group, and L¹ is an optionally substituted divalent organic group, and in general formula (2), R⁵ is a hydrogen atom or an optionally substituted alkyl group, X is a single bond or an optionally substituted divalent organic group, and L² is an optionally substituted divalent organic group).
 11. A method for producing a laminate having a metal film, the method comprising: an application step in which a photosensitive resin composition containing a polymer having a functional group capable of interacting with a plating catalyst or its precursor and a polymerizable group is applied onto a substrate to form a photosensitive resin composition layer on the substrate; an exposure step in which the photosensitive resin composition layer is exposed in a pattern shape to form a patterned cured layer; a development step in which part of the photosensitive resin composition layer unexposed in the exposure step is removed; a catalyst applying step in which the patterned cured layer obtained in the development step is contacted with the plating catalyst liquid according to claim 1 to apply the plating catalyst or its precursor to the cured layer; and a plating step in which a plating treatment is performed on the cured layer to which the plating catalyst or its precursor was applied in the catalyst applying step.
 12. The method for producing a laminate having a metal film according to claim 11, wherein the plating treatment in the plating step is one in which electroless plating is followed by electroplating.
 13. The plating catalyst liquid according to claim 2 which further comprises an acid.
 14. The plating catalyst liquid according to claim 2, wherein a plating target is made of a hydrophobic resin having a functional group capable of interacting with a plating catalyst or its precursor.
 15. The plating catalyst liquid according to claim 3, wherein a plating target is made of a hydrophobic resin having a functional group capable of interacting with a plating catalyst or its precursor. 